Sliding Bearing and Pump Device Using the Same

ABSTRACT

In a sliding bearing, load carrying capacity and bearing rigidity is increased without increasing a size of the bearing and the pressure of the fluid. The sliding bearing comprises a cylindrical-shaped sleeve supporting a rotatable shaft via fluid, and hydrostatic pressure pockets provided in the inner periphery of the sleeve. The hydrostatic pressure pockets constitute a plurality of rows of circumferentially disposed hydrostatic pressure pockets via orifices. At least one of the hydrostatic pressure pocket rows is arranged adjacently to each of both end portions of the inner periphery of the sleeve. And a circular cylindrical inner peripheral surface region without the hydrostatic pressure pockets is provided at a center portion of the sleeve. A width of the circular cylindrical inner peripheral surface region provided in the axial direction of the shaft is made wider than a sum of widths of the hydrostatic pressure pocket rows.

CLAIM OF PRIORITY

The present application claims priority from Japanese application serialNo. 2011-271887 filed on Dec. 13, 2011, the content of which is herebyincorporated by reference into this application

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sliding bearing provided with ahydrostatic pressure bearing structure in which high pressure fluid issupplied into a gap between the outer periphery of a shaft and the innerperiphery of a sleeve from the outside and which supports rotationalmovement of the shaft, and a pump device provided with a mechanism whichsupports, through the sliding bearing, the rotational movement of theshaft connected to an impeller.

2. Description of the Related Art

As a large-sized pump device used in, for example, a circulative coolingsystem of a fast-breeder reactor, there has been generally used amechanical-type vertical axial pump device in which an impeller attachedto a longitudinal shaft is rotation-moved in a casing, to therebytransfer fluid, such as fluid metal, that is a cooling medium.

In this pump device, for the purposes of preventing impinging of theimpeller on the casing or the like due to centrifugal whirling and/orearth quake, and suppressing vibration of the shaft, a journal bearingis arranged adjacently to the impeller of the shaft. As this journalbearing, there is often employed a sliding bearing. A shaft outerperiphery is slid relative to a substantially cylindrical-shaped sleeveinner periphery of the sliding bearing while being lubricated via thefluid, whereby the rotational movement of the shaft is supported.

In the sliding bearing used in such a pump device, for the purpose ofallowing thermal deformation and manufacturing tolerances of the shaftand casing, a gap between the shaft outer periphery and the bearinginner periphery is required to be increased relative to that in ageneral sliding bearing. Moreover, for the purpose of preventing theentrance of foreign material, fluid that can be used for the lubricationof the sliding bearing is limited to fluid of the same kind as the fluidto be transferred by the pump. In the pump device for the fast-breederreactor, use of low-viscosity fluid metal or the like is required.

In the aforesaid situation, the sliding bearing itself which is used inthe pump device is subjected to conditions where it is hard to obtainhigh dynamic pressure as compared to an oil lubricating sliding bearingused in a general mechanical device. Therefore, in order to stablysupport the shaft against high load even under such conditions, therehas been often employed a hydrostatic pressure bearing structure inwhich high pressure fluid is introduced onto a sliding surface from theoutside of the bearing and used to support a load.

Generally, in a journal bearing-type sliding bearing having thehydrostatic pressure bearing structure, several recess portions called“hydrostatic pressure pockets” are provided in a substantially circularcylindrical-shaped sleeve inner periphery in a circumferential directionor in a shaft axial direction and occupy the most part of the sleeveinner periphery. A passageway which communicates with an externalpressure source is opened in each of the hydrostatic pressure pockets.High pressure fluid which is introduced via the passageways into thehydrostatic pressure pockets from the external pressure source fillshydrostatic pressure pocket interiors and a gap between the bearing andthe shaft and flows to a low-pressure outside from an opened end portionof the gap.

If the shaft is radially pressed by a load and made eccentric in thebearing, a deviation of the gap is partially produced, so that theamount of fluid flowing out of a part of the gap present in an eccentricdirection is reduced and pressure in the part rises, while the amount offluid flowing out of a part of the gap present in a direction oppositeto the eccentric direction is increased and pressure in the part drops.Pressure difference between both parts generates a restoring forcetending to return the shaft to a center of the bearing, whereby the loadof the shaft is supported.

In recent years, according to capacity enlargement of the pump device,demand has been raised for improving a load carrying capacity that is asupportable load for the sliding bearing, and a bearing rigidity that isa load carrying capacity change relative to a minimum gap change due toshaft eccentricity.

JP-A No. 61-236921 disclosing the background art in this technical fielddescribes a hydrostatic pressure bearing which includes pockets in abearing inner peripheral surface and in which high pressure oil isadapted to be supplied between the pockets and the outer peripheralsurface of a rotating shaft. A plurality of pocket rows are formed in acircumferential direction arranged in an axial direction and the phasesof the pockets between the respective rows are shifted in thecircumferential direction.

According to the background art disclosed in JP-A No. 61-236921, theplurality of pocket rows in which the hydrostatic pressure pockets areformed in the circumferential direction is arranged in the axialdirection and the phases of the pockets between the respective rows areshifted in the circumferential direction, whereby when the shaft is madeeccentric in a certain radial direction, a force which acts in a radialdirection perpendicular to this is cancelled and it can be anticipatedthat stability of the bearing at the time of high speed rotation isimproved.

However, even if the phases of the hydrostatic pressure pockets areshifted in the circumferential direction and the pockets are merelyarranged in the plurality of rows as described in the patent literature1, this structure has little influence on the load carrying capacity andbearing rigidity of the bearing and it is hard for the structure toincrease the load carrying capacity without increasing the pressure ofan oil supplied from the outside, or without increasing the size of thebearing.

Moreover, JP-A No. 57-200699 describes a pump for fluid metal which isprovided with a bearing for an impeller shaft, arranged just adjacentlyto an impeller provided between an inlet port and an outlet port in acasing and in which plural pockets are circumferentially arranged in abearing inner surface and a portion of fuel metal pressed out by theimpeller is introduced into the pockets, in which circumferential recessgrooves that contain the fluid metal and allow the fluid metal to bepresent therein are provided in annular-band portions which axiallyinterpose the pockets and are provided so as to be relatively-rotatedwith liquid sealing properties.

Moreover, JP-A No. 57-200699 describes a pump in which ring-shapedcircumferential vacancies having the fluid metal always containedtherein are additionally provided in annular-band portions which areprovided so as to axially interpose the pockets constituting ahydrostatic pressure bearing for supporting the impeller and have liquidsealing properties.

According to the background art disclosed in JP-A No. 57-200699, thestructure in which the circumferential recess grooves are provided inthe annular-band portions that are provided so as to axially interposethe hydrostatic pressure pockets into which high pressure liquid metalis supplied from the outside is employed, whereby it is anticipated thateven when metal contact is produced between the shaft and the bearing,the fluid metal is easy to be supplied to the circumference of thecontacted portions and damage occurring due to seizure or the like isreduced by the effects of lubrication and cooling.

However, even if the circumferential recess grooves are provided in theannular-band portions as described in JP-A No. 57-200699, change inpressure distribution on a bearing inner periphery is small and theeffects of improving the load carrying capacity and bearing rigidity ofthe bearing cannot be anticipated at all. Therefore, it is hard toimprove the load carrying capacity without increasing the pressure of anoil supplied from the outside or without increasing the size of thebearing.

Moreover, JP-A No. 60-37329 describes a fluid bearing device in which aplurality of pressure generating band regions are formed in thecircumferential direction of a bearing surface that supports an axialload and is provided at a bearing member fixed relative to a rotatableshaft member and each of the pressure generating band regions comprisesa hydrostatic pressure generating portion including a pair of pocketsformed so as to be axially spaced and having excretion mechanisms, adynamic pressure generating portion including a land portion formed at amiddle between the both pockets, and a supply groove formed along a sideof the land which is parallel to axial lines of the both pockets,interconnecting the both pockets, and supplying pressure fluid to theboth pockets via a throttle, and a bearing gap of the dynamic pressuregenerating portion is made smaller than a bearing gap of the hydrostaticpressure generating portion.

According to the fluid bearing device disclosed in JP-A No. 60-37329, itcan be anticipated that in addition to the generation of hydrostaticpressure by the pressure fluid that is introduced into the externalsupply groove and also supplied to the pockets, the generation of thedynamic pressure in the dynamic pressure generating portion surroundedby the pockets and the supply groove can be also anticipated.

However, in the fluid bearing device disclosed in JP-A No. 60-37329,even if the dynamic pressure that is higher than the pressure of thepressure fluid supplied from the outside is produced in the dynamicpressure generating portion, the pressure is easy to escape through thesupply groove and supporting by the dynamic pressure is restricted.Therefore, the load carrying capacity considerably depends upon thehydrostatic pressure.

Moreover, if the shaft is deformed or inclined to thereby make a certainpart of the gap between the shaft and the bearing wider and an amount offluid flowing out of the widened part of the gap is increased, an entirepressure in the pockets and the supply groove which communicate witheach other is reduced and the load carrying capacity is easy to belowered. In the vertical-type pump device, the shaft rotates in a stateinclined relative to the bearing inner periphery in many cases.Therefore, it is difficult to apply the structures disclosed in thepatent literatures to the vertical-type pumps or the like.

The present invention has been made with a view of the aforesaidbackground and it is an object of the present invention to provide ajournal bearing-type sliding bearing provided with a hydrostaticpressure bearing structure in which high pressure fluid is supplied intoa gap between an outer periphery of a shaft and an inner periphery of asubstantially circular cylindrical shaped bearing from an outside andwhich supports rotational movement of the shaft, and a pump devicehaving the sliding bearing enclosed, in which dynamic pressure producedin the gap at the time of rotation of the shaft is increased andutilized to the fullest, whereby it is possible to increase the loadcarrying capacity and bearing rigidity of the bearing without increasinga size of the bearing and the pressure of the fluid supplied from theoutside.

SUMMARY OF THE INVENTION

In accordance with an aspect of the present invention, there is provideda sliding bearing which comprises a substantially circularcylindrical-shaped sleeve slidingly supporting a rotatable shaft viafluid in an inner periphery thereof, hydrostatic pressure supplyingpassages penetrating through the sleeve and supplying high pressurefluid into the sleeve inner periphery from an external pressure source,and hydrostatic pressure pockets provided in the inner periphery of thesleeve and having radially recessed shapes, the hydrostatic pressuresupplying passages being opened in the hydrostatic pressure pockets, inwhich the hydrostatic pressure pockets constitute a plurality of rows ofcircumferentially disposed hydrostatic pressure pockets, at least one ofthe hydrostatic pressure pocket rows being arranged adjacently to eachof both end portions of the inner periphery of the sleeve in an axialdirection of the shaft, and a circular cylindrical inner peripheralsurface region in which the hydrostatic pressure pockets are not presentis provided at a center portion of the sleeve so as to be interposedbetween the hydrostatic pressure pocket rows.

In a sliding bearing according to a preferred embodiment of the presentinvention, a width of the circular cylindrical inner peripheral surfaceregion without the hydrostatic pressure pockets which is provided in theaxial direction of the shaft may be made wider than a sum of widths ofthe hydrostatic pressure pocket rows which is provided in the axialdirection of the shaft.

In a sliding bearing according to a preferred embodiment of the presentinvention, hydrostatic pressure supplying passages communicating withhydrostatic pressure pockets belonging to the same hydrostatic pressurepocket row and hydrostatic pressure supplying passages communicatingwith hydrostatic pressure pockets belonging to a different hydrostaticpressure pocket row may be independently communicated with the pressuresource supplying the high pressure fluid.

In a sliding bearing according to a preferred embodiment of the presentinvention, an arrangement-angle range of hydrostatic pressure pocketswhich extends in a circumferential direction may have a shape that issuperposed on an arrangement-angle range of adjacent hydrostaticpressure pockets.

In a sliding bearing according to a preferred embodiment of the presentinvention, an arrangement-angle range of hydrostatic pressure pocketswhich extends in a circumferential direction may be located so as to besuperposed on an arrangement-angle range of adjacent hydrostaticpressure pockets.

In a sliding bearing according to a preferred embodiment of the presentinvention, each of the hydrostatic pressure pockets may have a shape inwhich an outer side of the hydrostatic pressure pocket that is adjacentto an end portion of the sleeve extends to an upstream side relative toa rotational direction of the shaft as compared to an inner side of thehydrostatic pressure pocket that is remote from the end portion of thesleeve and the inner side of the hydrostatic pressure pocket that isremote from the end of the sleeve extends to a downstream side relativeto the rotational direction of the shaft as compared to the outer sideof the hydrostatic pressure pocket that is adjacent to the end portionof the sleeve.

In a sliding bearing according to a preferred embodiment of the presentinvention, a region of the sleeve inner periphery that has nohydrostatic pressure pockets may be formed with grooves in which thehydrostatic pressure supplying passages are not opened.

According to another aspect of the present invention, there is provideda pump device which comprises an impeller arranged at a midway of afluid passage and transferring fluid according to rotational movementthereof, a shaft connected to an rotation power source androtation-driving the impeller, a sliding bearing provided with asubstantially circular cylindrical-shape sleeve slidingly supporting anouter peripheral surface of the shaft via the fluid, hydrostaticpressure supplying passages penetrating through the sleeve and supplyinghigh pressure fluid into an inner periphery of the sleeve from an outletside of the fluid passage.

The sliding bearing has hydrostatic pressure pockets which are providedin the inner periphery of the sleeve and have radially recessed shapes,the hydrostatic pressure supplying passages being opened in thehydrostatic pressure pockets, in which the hydrostatic pressure pocketsconstitute a plurality of rows of circumferentially disposed hydrostaticpressure pockets, at least one of the hydrostatic pressure pocket rowsbeing arranged adjacently to each of both end portions of the innerperiphery of the sleeve in an axial direction of the shaft, and acircular cylindrical inner peripheral surface region in which thehydrostatic pressure pockets are not present is provided at a centerportion of the sleeve so as to be interposed between the hydrostaticpressure pocket rows.

In a pump device according to a preferred embodiment of the presentinvention, a width of the circular cylindrical inner peripheral surfaceregion which is provided in an axial direction of the shaft may be madewider than a sum of widths of the hydrostatic pressure pocket rows whichis provided in the axial direction of the shaft.

In a pump device according to a preferred embodiment of the presentinvention, hydrostatic pressure supplying passages communicating withhydrostatic pressure pockets belonging to a hydrostatic pressure pocketrow and hydrostatic pressure supplying passages communicating withhydrostatic pressure pockets belonging to a different hydrostaticpressure pocket row may be independently communicated with the outletside of the fluid passage.

In a pump device according to a preferred embodiment of the presentinvention, the fluid that flows through the fluid passage may be fluidmetal.

According to the present invention, in the sliding bearing thatcomprises the substantially circular cylindrical-shaped sleeve slidinglysupporting the rotatable shaft via fluid in the inner periphery thereof,the hydrostatic pressure supplying passages penetrating through thesleeve and supplying high pressure fluid into the sleeve inner peripheryfrom the external pressure source, and the hydrostatic pressure pocketsprovided in the inner periphery of the sleeve and having radiallyrecessed shapes, the hydrostatic pressure supplying passages beingopened in the hydrostatic pressure pockets, the hydrostatic pressurepockets constitute the plurality of rows of circumferentially disposedhydrostatic pressure pockets, the at least one of the hydrostaticpressure pocket rows is arranged adjacently to each of both end portionsof the inner periphery of the sleeve in the axial direction of theshaft, and the circular cylindrical inner peripheral surface region inwhich the hydrostatic pressure pockets are not present is provided atthe center portion of the sleeve so as to be interposed between thehydrostatic pressure pocket rows.

Therefore, the shaft that is rotated in the inner periphery of thesleeve is supported by the hydrostatic pressure supplied in thehydrostatic pressure pockets from the outside and dynamic pressureproduced on the circular cylindrical inner peripheral surface region.When the dynamic pressure is produced, large pressure is obtained ascompared to the conventional example, and the loading capability andbearing rigidity of the entire sliding bearing can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structure view of a vertical-type pump device according toan embodiment 1 of the present invention;

FIG. 2 is an enlarged view of a circumference of a sliding bearing inthe vertical-type pump device according to the embodiment 1 of thepresent invention;

FIG. 3 is a perspective view of a sleeve in the sliding bearingaccording to the embodiment 1 of the present invention;

FIG. 4 is a graph showing a loading capability in the sliding bearingaccording to the embodiment 1 of the present invention;

FIG. 5 is a graph showing a bearing rigidity in the sliding bearingaccording to the embodiment 1 of the present invention;

FIG. 6 is a sectional view of a sliding bearing according to anembodiment 2 of the present invention;

FIG. 7 is a sectional view of a sliding bearing according to anembodiment 3 of the present invention;

FIG. 8 is a sectional view of a sliding bearing according to anembodiment 4 of the present invention;

FIG. 9 is a sectional view of a sliding bearing according to anembodiment 5 of the present invention; and

FIG. 10 is a sectional view of a sliding bearing according to anembodiment 6 of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be explained hereinafter withreference to the drawings.

Embodiment 1

An embodiment 1 of the present invention will be explained withreference to a vertical-type pump device 100 having a journalbearing-type sliding bearing according to the present inventionincorporated therein.

FIG. 1 is a structure view of the vertical-type pump device 100according to this embodiment. A passage 104 which communicates betweenan inlet port 102 and an outlet port 103 is formed in the interior of acasing 101. At the midway of the passage 104, an impeller 105 isprovided at a tip end of a shaft 106 connected to an external rotationpower source 107.

The shaft 106 is rotatably supported, on a side thereof adjacent to therotation power source 107, by a bearing 108, and is rotatably supported,on a side thereof adjacent the impeller 105, by a sliding bearing 109.Supply of power from the rotation power source 107 causes the shaft 106to be rotated to rotation-move the impeller 105, whereby fluid such asfluid metal which flows into an interior of the pump device 100 from theinlet port 102 is transferred through the passage 104 and thendischarged out of the outlet port 103. Pressure head is produced at adownstream side of the passage 104 relative to the impeller 105, ascompared to an upstream side of the passage 104 relative to the impeller105, and pressure at the upstream side is increased.

The bearing 108 of the two bearings rotatably supports the shaft 106 andsupports load produced in a vertical direction of FIG. 1, i.e., in anaxial direction of the shaft 106. On the other hand, the sliding bearing109 is fixed to a support portion 110 and suppresses centrifugalwhirling of the shaft in a radial direction, to thereby suppressvibration produced according to the rotational movement of the shaft 106and impeller 105, in addition to preventing impingement of the impeller105 against a wall surface of the passage 104, the casing 101, etc.

FIG. 2 is an enlarged view of a circumference of a sliding bearing 109.In the sliding bearing 109, several hydrostatic pressure pockets 112Athat have concavities recessed in the radial direction are formed in aninner periphery of a substantially circular cylindrical-shaped sleeve111A. Hydrostatic pressure supplying passages 113 which penetratethrough the support portion 110 and the sleeve 111A from the outlet portside of the passage 104 are opened in the respective hydrostaticpressure pockets 112A via orifices 114.

Thereby, portions of high pressure fluid that have been transferred tothe downstream side of the passage 104 by the rotation of the impeller105 pass through the hydrostatic pressure supplying passages 113 and theorifices 114, are introduced into the hydrostatic pressure pockets 112A,and fill a gap between the outer periphery of the shaft 106 and theinner periphery of the sleeve 111A.

The hydrostatic pressure pockets 112A constitute a plurality of rows ofcircumferentially disposed hydrostatic pressure pockets 112A in theinner periphery of the sleeve 111A. One row of hydrostatic pressurepockets is formed adjacently to each of the both end portions of theinner periphery of the sleeve 111A in the axial direction of the shaft106. Moreover, a circular cylindrical inner peripheral surface region115 in which a row of hydrostatic pressure pockets is not present isprovided at a center portion of the inner periphery of the sleeve 111Aso as to be interposed between the rows of hydrostatic pressure pockets.

FIG. 3 is a perspective view illustrating a detail of the sleeve 111A.The inner periphery of the sleeve 111A is provided at each of the bothend portions thereof with the one row 116 of circumferentially disposedhydrostatic pressure pockets 112A, while the outer periphery of thesleeve 111A is provided with the hydrostatic pressure supplying passages113.

A hydrostatic pressure supplying passage 113 communicating with one ofthe hydrostatic pressure pocket rows 116 and a hydrostatic pressuresupplying passage 113 communicating with the other of the hydrostaticpressure pocket rows 116 are provided independently from each other andseparately communicate with the downstream side of the passage 104 asalso shown in FIG. 2.

The inventor of the present invention made the sliding bearing accordingto the present invention, performed an evaluation on loading capabilityand bearing rigidity, verified improvement effects of the loadingcapability and bearing rigidity by the application of the presentinvention, and investigated a relationship between the hydrostaticpressure pockets 112A capable of effectively achieving load reductionand effectively improving the bearing rigidity, and the circularcylindrical inner peripheral surface region 115 interposed by thehydrostatic pressure rows 116. Next, the results will be explained withreference to FIGS. 4 and 5.

FIG. 4 shows the loading capability of the bearing in a case where thepressure of the fluid supplied to the hydrostatic pressure pockets 112Ais made constant and the widths of the hydrostatic pressure pockets 112Aand the width of the circular cylindrical inner peripheral surfaceregion 115 in the inner periphery of the sleeve 111A are varied. Whenthe width of the circular cylindrical inner peripheral surface region115 is increased relative to the sum of the widths of the hydrostaticpressure pocket rows 116 provided adjacently to the both ends of thesleeve 111A so as to interpose the circular cylindrical inner peripheralsurface region 115 therebetween, the increase has resulted in particularin improvement of a loading capability increasing rate of the bearing ascompared to a case of being equal to or lower than it.

FIG. 5 shows the bearing rigidity in the case where the pressure of thefluid supplied to the hydrostatic pressure pockets 112A is made constantand the widths of the hydrostatic pressure pockets 112A and the width ofthe circular cylindrical inner peripheral surface region 115 in theinner periphery of the sleeve 111A are varied. When the width of thecircular cylindrical inner peripheral surface region 115 is increasedrelative to the sum of the widths of the hydrostatic pressure pocketrows 116 provided adjacently to the both ends of the sleeve 111A so asto interpose the circular cylindrical inner peripheral surface region115 therebetween, the increase has resulted in particular in improvementof a bearing rigidity increasing rate as compared to a case of beingequal to or lower than it.

When the hydrostatic pressure pockets rows 116 to be arranged adjacentlyto the both end portions of the inner periphery of the sleeve 111A andthe circular cylindrical inner peripheral surface region 115 to beinterposed between the hydrostatic pressure pocket rows 116 are formed,if the width of the circular cylindrical inner peripheral surface region115 in the axial direction of the shaft 106 is increased, in this way,relative to the sum of the widths of the hydrostatic pressure pocketrows 116 interposing the circular cylindrical inner peripheral surfaceregion, it has been verified that the load carrying capacity and thebearing rigidity can be more effectively increased.

Embodiment 2

The main purpose of providing the hydrostatic pressure pocket rowsadjacently to the both end portions of the inner periphery of the sleevelies in that pressure at the both ends of the circular cylindrical innerperipheral surface region arranged so as to be interposed between thehydrostatic pressure pocket rows is kept in a high state and a level ofthe dynamic pressure produced on the circular cylindrical innerperipheral surface region is kept.

FIG. 6 shows an embodiment 2 of a sleeve portion of a sliding bearingthat more positively attains this purpose. Two hydrostatic pressurepocket rows 116 are arranged adjacently to each of the both end portionsof the inner periphery of a sleeve 111B. In the two adjacent hydrostaticpressure pocket rows 116, hydrostatic pressure pockets 112B are arrangedso as to be staggered in the circumferential direction.

A circular cylindrical inner peripheral surface region 115 in which thehydrostatic pressure pockets 112B are not present is formed at a centerportion of the inner periphery of the sleeve 111B. The width of thecircular cylindrical inner peripheral surface region 115 in the axialdirection of the shaft 106 is wider than the sum of the widths of thefour hydrostatic pressure pocket rows 116 interposing the circularcylindrical inner peripheral surface region 115 on the both sidesthereof.

When such a structure is employed, at a circumferentially angularposition in which the hydrostatic pressure pocket is not present in onehydrostatic pressure row 116, the hydrostatic pressure pockets 112Bwhich belong to another adjacent hydrostatic pressure pocket row 116 arelocated, and the supply of the hydrostatic pressure by the hydrostaticpressure pockets 112B is uniformly successively performed in the wholecircumferences of the both end portions of the sleeve 111B. Thereby, thepressure on the circular cylindrical inner peripheral surface region 115is kept in a higher state and it is possible to provide high loadingcapability and bearing rigidity to the sliding bearing.

Embodiment 3

FIG. 7 shows an embodiment 3 of a sleeve portion of a sliding bearingwhich increases pressure on neighborhoods of the both end portions of asleeve 111C, i.e., the both ends of the circular cylindrical innerperipheral surface region 115. Hydrostatic pressure pockets 112C haveshapes asymmetrical in the circumferential direction and in the axialdirection of the shaft 106. Hydrostatic pressure pocket-extendingportions 117 are partially provided at the both ends of the hydrostaticpressure pockets 112C in the circumferential direction. Hydrostaticpressure pocket-extending portions 117 of a hydrostatic pressure pocket112C are separated from hydrostatic pressure pocket-extending portions117 of a circumferentially adjacent hydrostatic pressure pocket 112C butare partially superposed on them within a fixed circumferentialarrangement-angle range.

Each hydrostatic pressure pocket 112C is formed with a hydrostaticpressure pocket-extending portion 117 extending to the upstream side ofa rotational direction 118 of the shaft 106 on the outer side adjacentto the end portion of the sleeve 111C, and a hydrostatic pressurepocket-extending portion 117 extending to the downstream side of therotational direction 118 of the shaft 106 on the inner side apart fromthe end portion of the sleeve 111C.

When such a structure is employed, the supply of the hydrostaticpressure by the hydrostatic pressure pockets 1120 is uniformlysuccessively performed in the whole circumferences of the both endportions of the sleeve 111C. Thereby, the pressure on the circularcylindrical inner peripheral surface region 115 is kept in a high stateand it is possible to provide high load carrying capacity and bearingrigidity to the bearing.

Moreover, small regions of the circumferential end portions of thehydrostatic pressure pockets 112C may be merely machined to thereby formthe hydrostatic pressure pocket-extending portions 117, so that themanufacturing cost of this embodiment is reduced as compared to theembodiment of FIG. 6 in which the four hydrostatic pressure pocket rowsin total are provided.

Moreover, the inner side of the sleeve 111C extends on the downstreamside of the rotational direction of the shaft 106, so that a suckingforce that tends to draw the fluid in the hydrostatic pressure pockets112C toward the center side of the sleeve 111C acts according to therotation of the shaft 106 and higher pressure is easy to be kept on thecircular cylindrical inner peripheral surface region 115.

Embodiment 4

Similarly, FIG. 8 shows an embodiment 4 of a sleeve portion of a slidingbearing which increases pressure on neighborhoods of the both endportions of the inner periphery of a sleeve 111D, i.e., the both ends ofa circular cylindrical inner peripheral surface region 115. Forming ofhydrostatic pressure pockets 112D into rhombus shapes is performed inlieu of forming the hydrostatic pressure pocket-extending portions 117at the hydrostatic pressure pockets 112D as in the embodiment shown inFIG. 7. The hydrostatic pressure pockets 112D are smoothly extended tothe upstream side of the rotational direction 118 of the shaft 106,according to progressing toward the outer sides thereof that areadjacent to the end portions of the sleeve 111D, and are smoothlyextended to the downstream side in the circumferential directionaccording to progressing toward the inner sides thereof that are remotefrom the end portions of the sleeve 111D.

When such a structure is employed, a sucking force that tends to drawthe fluid in the hydrostatic pressure pockets 112D toward the centerside of the sleeve 111D is easier to act as compared to the embodimentshown in FIG. 7, so that higher pressure is easy to be kept on thecircular cylindrical inner peripheral surface region 115.

Embodiment 5

Moreover, FIG. 9 shows an embodiment in which foreign materialdischarging grooves 119 are formed in portions of the inner periphery ofa sleeve 111E in which hydrostatic pressure pockets 112E are notpresent. The foreign material discharging grooves 119 are provided in acircular cylindrical inner peripheral surface region 115 occupying thecenter portion of the sleeve 111E, and regions of the both end portionsof the sleeve 111E in which the hydrostatic pressure pockets 112E arenot present. The foreign material discharging grooves 119 are grooveswhich are recessed in a radial direction different from a recesseddirection of the hydrostatic pressure pockets 112E and in which theorifices 114 are not opened.

If any foreign material, wear particles, etc. flow into and remain in agap between the outer periphery of the shaft 106 and the inner peripheryof the sleeve 111E, the shaft 106 and/or the sleeve 111E may be subjectto wear and/or damage. When the structure shown in FIG. 9 is employed,discharging of the foreign material, wear particles, etc. flowing intothe gap between the outer periphery of the shaft 106 and the innerperiphery of the sleeve 111E is facilitated.

The orifices 114 are not opened in the foreign material discharginggrooves 119, and the foreign material discharging grooves 119 do notcommunicate directly with hydrostatic pressure supplying passages 113,so that dynamic pressure that is produced on the circular cylindricalinner peripheral surface region 115 escapes via the hydrostatic pressuresupplying passages 113, resulting in less effect on the reduction in thepressure on the circular cylindrical inner peripheral surface region115.

Moreover, the sizes of the foreign material, the wear particles, etc.flowing into the gap between the outer periphery of the shaft 106 andthe inner periphery of the sleeve 111E are sizes at most equal to thesize of the gap, so that the depths of the foreign material discharginggrooves 119 may be also about equal to the size of the gap. Therefore,when the depths of the foreign material discharging grooves 119 are madeabout equal to the size of the gap, even if they extend up to the endsof the sleeve 111E, enlargement of clearance sectional areas in the endportions is small and escapement of the pressure through this route canbe reduced.

Thereby, it is possible to configure a high reliable bearing in whichthe shaft 106 and/or the sleeve 111E is unlikely to be subject to damagedue to the foreign material, the wear particles, etc., while providinghigh loading capability and bearing rigidity to the sliding bearing.

Embodiment 6

Moreover, FIG. 10 shows an embodiment 6 in which grooves 120 in whichthe orifices 114 are not opened are formed in the circular cylindricalinner peripheral surface region 115. Each groove 120 is extended, on theouter side thereof more adjacent to the end portion of a sleeve 111F, tothe upstream side in the rotational direction 118 of the shaft 106, andis extended, on the inner side thereof away from the end portion of thesleeve 111F, to the downstream side in the rotational direction 118 ofthe shaft 106.

When such a structure is employed, a flow of the fluid is easy to becometurbulence on the circular cylindrical inner peripheral surface region115, or a sucking force that tends to draw the fluid toward the centerportion of the sleeve 111F is easier to act according to the rotation ofthe shaft 106, so that an effect of generating dynamic pressure isincreased.

Moreover, it is possible to configure a high reliable sliding bearingwhich may not be subject to the damage of the shaft 106 and/or sleeve111F which occurs due to the accumulation of the foreign material, wearparticles, etc. in the grooves 120.

As apparently noted from the above embodiments, the sliding bearingaccording to the present invention employs the structure in which thefixed circular cylindrical inner peripheral surface region is obtainedat the center portion of the inner periphery of the sleeve and thehydrostatic pressure pocket rows are disposed at the both end portionsof the sleeve so as to interpose the circular cylindrical innerperipheral surface region therebetween, whereby the pressure on thecircular cylindrical inner peripheral surface region on which thedynamic pressure is produced at the time of the shaft rotation isincreased and high pressure is kept by the circular cylindrical innerperipheral surface region, to thereby improve the loading capability andthe bearing rigidity.

Moreover, the hydrostatic pressure supplying passages are independentlyprovided at the both end portions of the sleeve and are separatelycommunicated with the pressure source that can supply the adequatequantity of high pressure fluid, whereby the effect of the reduction ofthe pressure in the specific hydrostatic pressure pocket row on otherpocket rows is restricted and high loading capability and bearingrigidity are obtained even if the shaft is brought to a state where itis inclined relative the inner periphery of the sleeve or deformed.

Moreover, the circular cylindrical inner peripheral surface region inthe inner periphery of the sleeve is arranged so as to be interposed inthe shaft axial direction by the hydrostatic pressure pocket rows, inwhich the pressure is higher than the pressure in the opened endportions of the sleeve, and the width of the circular cylindrical innerperipheral surface region is made wider than the sum of the widths ofthe hydrostatic pressure pocket rows that are provided in the shaftaxial direction, whereby in addition to the increase in the pressure onthe circular cylindrical inner peripheral surface region at the time ofthe shaft rotation, a ratio of dependency of the load carrying capacityon the pressure produced on the circular cylindrical inner peripheralsurface region at the time of the eccentricity of the shaft isincreased.

Therefore, even if the supply pressure from the outside is notincreased, or even if the gap between the outer periphery of the shaftand the inner periphery of the sleeve is not made narrow, or even if thesize of the sleeve is not increased, the loading capability and bearingrigidity of the entire sliding bearing can be effectively increased.

Moreover, according to the structure in which the hydrostatic pressurepocket rows are respectively provided adjacently to the both endportions of the sleeve, and the hydrostatic pressure supplying passagesthat are respectively communicated with the pocket rows are madeindependent from one another and connected to the pressure sourcecapable of supplying the adequate quantity of high pressure, even if aspecific part of the gap is widened by the inclination of the shaft andthe pressure in the hydrostatic pressure pockets around the specificpart of the gap is reduced.

The reduction does not effect on other hydrostatic pressure pocket rows,in addition to producing of a moment force tending to return the postureof the shaft to its original posture even if the shaft is inclined inthe sleeve, so that it is possible to obtain high loading capability andbearing rigidity even at the time of the inclination of the shaft.

Moreover, the pump device according to the present invention has thestructure which encloses the sliding bearing according to the presentinvention and supplies the pressure fluid to the hydrostatic pressurepockets from the outlet port side of the pump device, so that anadditional pump device for supplying the pressure fluid to thehydrostatic pressure pockets is not required, thus making it possible tominiaturize the system.

Moreover, even if the gap between the outer periphery of the shaft andthe inner periphery of the sleeve is made wider in a certain degree, orthe shaft is inclined at a certain degree in the sleeve, it is possibleto produce and keep, on the circular cylindrical inner peripheralsurface region, the dynamic pressure higher than the pressure of thefluid supplied to the hydrostatic pressure pockets from the pump device.

Thereby, even in the large-sized pump device, in which the rotationalmovement of the shaft is required to be stably supported against thelarge thermal deformation, the manufacturing tolerances, etc., such asthe vertical axial pump device used in the circulative cooling system ofthe fast breeder reactor, the high loading capability and bearingrigidity of the bearing can be obtained and the high reliability can beobtained.

For example, in the circulative cooling system of the fast breederreactor, fluid such as liquid sodium or the like is often used as acooling medium. In the pump device for transferring fluid metal, thesame fluid metal is required to be used for lubrication in order that itis prevented from being mixed with other substances.

Generally, the fluid metal has a nature exhibiting a viscosity lowerthan that of a lubricating oil for a general machine or water at a hightemperature, and is poor in lubricity.

Moreover, in the pump device, in addition to the requirement of makingthe shaft for rotating the impeller longitudinal in order to provide ashielding portion for radiation, it is hard to avoid the inclination anddeformation of the shaft in a certain degree due to the thermaldeformation and/or manufacturing tolerance since the pump device handleshigh temperature fluid metal.

In the pump device according to the present invention, the fluid that isbrought into the high pressure by the impeller of the pump device issupplied to the hydrostatic pressure pockets of the sliding bearingenclosed, so that other substances may not get mixed with the coolingmedium in the pump device.

Moreover, according to the structure in which the fixed circularcylindrical inner peripheral surface region is obtained at the center ofthe sleeve inner periphery in the sliding bearing and the hydrostaticpressure pocket rows are arranged at the both end portions of the sleeveso as to interpose the circular cylindrical inner peripheral surfaceregion, the pressure on the circular cylindrical inner peripheralsurface region on which the dynamic pressure is produced at the time ofthe shaft rotation is increased and the high pressure is kept by thecircular cylindrical inner peripheral surface region, whereby it ispossible to obtain the high load carrying capacity and bearing rigidityeven in the case where a low viscosity fluid such as fluid metal whichis poor in lubricity is used.

The load carrying capacity of the sliding bearing considerably dependsupon the dynamic pressure particularly at the time when the shaft ismade eccentric and it is unnecessary to externally install any devicefor particularly increasing the pressure of the fluid supplied to thebearing, in order to obtain the loading capability. Therefore, it ispossible to make the pump device simple and small-sized.

Moreover, even if the gap between the shaft outer periphery and thesleeve inner periphery is made relatively wide, or in the case where theshaft is brought to the posture inclined relative to the sleeve innerperiphery or deformed, the high loading capability and bearing rigidityare obtained, so that the thermal deformation and/or tolerance at thetime of manufacturing are allowed and the stable supporting of the shaftrotation is performed.

Moreover, the hydrostatic pressure pockets are arranged adjacently tothe end portions of the sleeve inner periphery, so that even in a casewhere excessive load acts on the shaft and the shaft that is inclinedrelative to the neighborhoods of the end portions of the sleeve innerperiphery is directly brought into contact with the sleeve innerperiphery, the fluid is supplied to the circumference to perform coolingand lubrication, thus making it to reduce damage due to wearing and/orseizure.

What is claimed is:
 1. A sliding bearing comprising a substantiallycircular cylindrical-shaped sleeve slidingly supporting a rotatableshaft via fluid in an inner periphery thereof, hydrostatic pressuresupplying passages penetrating through the sleeve and supplying highpressure fluid into the sleeve inner periphery from an external pressuresource, and hydrostatic pressure pockets provided in the inner peripheryof the sleeve and having radially recessed shapes, the hydrostaticpressure supplying passages being opened in the hydrostatic pressurepockets, wherein the hydrostatic pressure pockets constitute a pluralityof rows of circumferentially disposed hydrostatic pressure pockets, atleast one of the hydrostatic pressure pocket rows being arrangedadjacently to each of both end portions of the inner periphery of thesleeve in an axial direction of the shaft, and a circular cylindricalinner peripheral surface region in which the hydrostatic pressurepockets are not present is provided at a center portion of the sleeve soas to be interposed between the hydrostatic pressure pocket rows.
 2. Thesliding bearing according to claim 1, wherein a width of the circularcylindrical inner peripheral surface region without the hydrostaticpressure pockets provided in the axial direction of the shaft is madewider than a sum of widths of the hydrostatic pressure pocket rowsprovided in the axial direction of the shaft.
 3. The sliding bearingaccording to claim 1, wherein hydrostatic pressure supplying passagescommunicating with hydrostatic pressure pockets belonging to the samehydrostatic pressure pocket row and hydrostatic pressure supplyingpassages communicating with hydrostatic pressure pockets belonging to adifferent hydrostatic pressure pocket row are independently communicatedwith the pressure source supplying the high pressure fluid.
 4. Thesliding bearing according to claim 1, wherein an arrangement-angle rangeof hydrostatic pressure pockets which extends in a circumferentialdirection has a shape that is superposed on an arrangement-angle rangeof adjacent hydrostatic pressure pockets.
 5. The sliding bearingaccording to claim 1, wherein an arrangement-angle range of hydrostaticpressure pockets which extends in a circumferential direction is locatedso as to be superposed on an arrangement-angle range of adjacenthydrostatic pressure pockets.
 6. The sliding bearing according to claim1, wherein each of the hydrostatic pressure pockets has a shape in whichan outer side of the hydrostatic pressure pocket that is adjacent to anend portion of the sleeve extends to an upstream side relative to arotational direction of the shaft as compared to an inner side of thehydrostatic pressure pocket that is remote from the end portion of thesleeve and the inner side of the hydrostatic pressure pocket that isremote from the end of the sleeve extends to a downstream side relativeto the rotational direction of the shaft as compared to the outer sideof the hydrostatic pressure pocket that is adjacent to the end portionof the sleeve.
 7. The sliding bearing according to claim 1, wherein aregion of the sleeve inner periphery that has no hydrostatic pressurepockets is formed with grooves in which the hydrostatic pressuresupplying passages are not opened.
 8. A pump device comprising animpeller arranged at a midway of a fluid passage and transferring fluidaccording to rotational movement thereof, a shaft connected to anrotation power source and rotation-driving the impeller, a substantiallycircular cylindrical-shape sleeve slidingly supporting an outerperipheral surface of the shaft via the fluid, hydrostatic pressuresupplying passages penetrating through the sleeve and supplying highpressure fluid into an inner periphery of the sleeve from an outlet sideof the fluid passage, and a sliding bearing having hydrostatic pressurepockets which are provided in the inner periphery of the sleeve and haveradially recessed shapes, the hydrostatic pressure supplying passagesbeing opened in the hydrostatic pressure pockets, wherein thehydrostatic pressure pockets constitute a plurality of rows ofcircumferentially disposed hydrostatic pressure pockets, at least one ofthe hydrostatic pressure pocket rows being arranged adjacently to eachof both end portions of the inner periphery of the sleeve in an axialdirection of the shaft, and a circular cylindrical inner peripheralsurface region in which the hydrostatic pressure pockets are not presentis provided at a center portion of the sleeve so as to be interposedbetween the hydrostatic pressure pocket rows.
 9. The pump deviceaccording to claim 8, wherein a width of the circular cylindrical innerperipheral surface region which is provided in an axial direction of theshaft is made wider than a sum of widths of the hydrostatic pressurepocket rows which is provided in the axial direction of the shaft. 10.The pump device according to claim 8, wherein hydrostatic pressuresupplying passages communicating with hydrostatic pressure pocketsbelonging to a hydrostatic pressure pocket row and hydrostatic pressuresupplying passages communicating with hydrostatic pressure pocketsbelonging to a different hydrostatic pressure pocket row areindependently communicated with the outlet side of the fluid passage.11. The pump device according to claim 8, wherein the fluid that flowsthrough the fluid passage is fluid metal.